The present invention relates to light string sets of the type having incandescent lamps and, more particularly, to a miniaturized light string set employing series-connected shunt-type incandescent lamps and a fusing arrangement.
The present invention is an improvement of the fused decorative string set described and claimed in Lehmann et al. U.S. Pat. No. 3,968,398 issued July 6, 1976.
Said Lehmann et al. patent disclosed a series-connected decorative incandescent lamp string set permitting the use of fine gauge wire in a series lamp circuit. Lamps at the end of the series string which were of an unshunted type whereas the remaining lamps in the series string were of a shunted type permitting continued current flow to the lamp in the event of filament burnout. The unshunted lamps at each end of the string were intended to serve as a fuse for the entire set, since the fine gauge wire (e.g., 24-gauge) interconnecting the shunted incandescent lamps was of insufficient size to be adequately protected by normal utility fuses in conventional 15- and 24-ampere branch circuits which, in normal practice, supply AC power to such string sets and other AC appliances connected at normal AC receptacles.
A problem attendant to the use of the string set disclosed and claimed in said Lehmann et al. patent is that tandem stringing of light sets was precluded. If a Christmas tree or the like was desired to be strung with multiple string sets, all of the plugs of each of the string sets had to be connected at approximately the same location to a source of power. Use of such arrangement is extremely awkward, at best, for the stringing of a large tree with lights since it is desirable if several strings are to be used that each successive string be connected in tandem to the end of the preceding string, i.e. so as to provide continuous end-to-end stringing.
Another difficulty inherent in the Lehmann et al. construction was that the plural use of light string sets, all connected at the same location, to an AC utility service provided no protection against the possibility that plural stringing of lights might cause excessive use of current such as to constitute a heavy electrical load.
Accordingly, among the several objects of the present invention may be noted the provision of an improved light string set; the provision of such a light string set utilizing miniature incandescent lamps; the provision of such a light string set permitting tandem stringing of lights interconnecting individual light sets of the character described in end-to-end relationship; the provision of such a light string set permitting the optimal use of fuse lamps to provide short circuit protection of a series string of incandescent lamps, a related object being the provision of such a light string set permitting the use of series interconnection of a plurality of miniature incandescent lamps by relatively fine gauge wire. A related object is the provision of such a light string set permitting tandem stringing of successive light string sets even though fine gauge wire is utilized to provide a series circuit interconnection of incandescent lamps of each such string.
Another object of the invention is the provision of a light string set which is fused to provide protection against a short-circuit or excessive current flow into the set, a related object being the provision of such a fused set which is of a universal configuration amenable to alternative fusing embodiments as desired in ultimate configuration so as to facilitate manufacturing.
Other objects of the invention include the provision of a light string set utilizing miniature lamps which are easily changed in the event of lamp burnout; the provision of such a light string set which is extremely attractive and pleasing to the eye, producing a sparkling optical effect from each lamp; and the provision of such light set which is conducive to extremely economical manufacture through the use of low cost materials and simplicity of construction.
Other objects will be in part apparent and in part pointed out in the following description.